This invention relates generally to the structure of soles of shoes and other footwear, including soles of street shoes, hiking boots, sandals, slippers, and moccasins. More specifically, this invention relates to the structure of athletic shoe soles, including such examples as basketball and running shoes.
Still more particularly, this invention relates to variations in the structure of such soles using a theoretically ideal stability plane as a basic concept.
The applicant has introduced into the art the concept of a theoretically ideal stability plane as a structural basis for shoe sole designs. The theoretically ideal stability plane was defined by the applicant in previous copending applications as the plane of the surface of the bottom of the shoe sole, wherein the shoe sole conforms to the natural shape of the wearer""s foot sole, particularly its sides, and has a constant thickness in frontal or transverse plane cross sections. Therefore, by definition, the theoretically ideal stability plane is the surface plane of the bottom of the shoe sole that parallels the surface of the wearer""s foot sole in transverse or frontal plane cross sections.
The theoretically ideal stability plane concept as implemented into shoes such as street shoes and athletic shoes is presented in U.S. Pat. Nos. 4,989,349, issued Feb. 5, 1991 and U.S. Pat. No. 5,317,819, issued Jun. 7, 1994, both of which are incorporated by reference, as well as U.S. Pat. No. 5,544,429 issued Aug. 13, 1996; U.S. Pat. No. 4,989,349 issued from U.S. patent application Ser. No. 07/219,387, U.S. Pat. No. 5,317,819 issued from U.S. patent application Ser. No. 07/239,667.
This new invention is a modification of the inventions disclosed and claimed in the earlier applications and develops the application of the concept of the theoretically ideal stability plane to other shoe structures. Each of the applicant""s applications is built directly on its predecessors and therefore all possible combinations of inventions or their component elements with other inventions or elements in prior and subsequent applications have always been specifically intended by the applicant. Generally, however, the applicant""s applications are generic at such a fundamental level that it is not possible as a practical matter to describe every embodiment combination that offers substantial improvement over the existing art, as the length of this description of only some combinations will testify.
Accordingly, it is a general object of this invention to elaborate upon the application of the principle of the theoretically ideal stability plane to the shoe structures.
The purpose of this application is to specifically describe some of the most important combinations, especially those that constitute optimal ones.
Existing running shoes are unnecessarily unsafe. They profoundly disrupt natural human biomechanics. The resulting unnatural foot and ankle motion leads to what are abnormally high levels of running injuries.
Proof of the unnatural effect of shoes has come quite unexpectedly from the discovery that, at the extreme end of its normal range of motion, the unshod bare foot is naturally stable, almost unsprainable, while the foot equipped with any shoe, athletic or otherwise, is artificially unstable and abnormally prone to ankle sprains. Consequently, ordinary ankle sprains must be viewed as largely an unnatural phenomena, even though fairly common. Compelling evidence demonstrates that the stability of bare feet is entirely different from the stability of shoe-equipped feet.
The underlying cause of the universal instability of shoes is a critical but correctable design flaw. That hidden flaw, so deeply ingrained in existing shoe designs, is so extraordinarily fundamental that it has remained unnoticed until now. The flaw is revealed by a novel new biomechanical test, one that is unprecedented in its simplicity. It is easy enough to be duplicated and verified by anyone; it only takes a few minutes and requires no scientific equipment or expertise. The simplicity of the test belies its surprisingly convincing results. It demonstrates an obvious difference in stability between a bare foot and a running shoe, a difference so unexpectedly huge that it makes an apparently subjective test clearly objective instead. The test proves beyond doubt that all existing shoes are unsafely unstable.
The broader implications of this uniquely unambiguous discovery are potentially far-reaching. The same fundamental flaw in existing shoes that is glaringly exposed by the new test also appears to be the major cause of chronic overuse injuries, which are unusually common in running, as well a other sport injuries. It causes the chronic injuries in the same way it causes ankle sprains; that is, by seriously disrupting natural foot and ankle biomechanics.
These and other objects of the invention will become apparent from a detailed description of the invention which follows taken with the accompanying drawings.
In its simplest conceptual form, the applicant""s invention is the structure of a conventional shoe sole that has been modified by having its sides bent up so that their inner surface conforms to a shape nearly identical (instead of the shoe sole sides being flat on the ground, as is conventional). This concept is like that described in FIG. 3 of the applicant""s 5,317,819 Patent (xe2x80x9cthe ""819 patentxe2x80x9d); for the applicant""s fully contoured design described in FIG. 15 of the ""819 patent, the entire shoe solexe2x80x94including both the sides and the portion directly underneath the footxe2x80x94is bent up to conform to a shape nearly identical but slightly smaller than the contoured shape of the unloaded foot sole of the wearer, rather than the partially flattened load-bearing foot sole shown in FIG. 3.
This theoretical or conceptual bending up must be accomplished in practical manufacturing without any of the puckering distortion or deformation that would necessarily occur if such a conventional shoe sole were actually bent up simultaneously along all of its the sides; consequently, manufacturing techniques that do not require any bending up of shoe sole material, such as injection molding manufacturing of the shoe sole, would be required for optimal results and therefore is preferable.
It is critical to the novelty of this fundamental concept that all layers of the shoe sole are bent up around the foot sole. A small number of both street and athletic shoe soles that are commercially available are naturally contoured to a limited extent in that only their bottom soles, which are about one quarter to one third of the total thickness of the entire shoe sole, are wrapped up around portions of the wearers"" foot soles; the remaining soles layers, including the insole, midsole and heel lift (or heel) of such shoe soles, constituting over half of the thickness of the entire shoe sole, remains flat, conforming to the ground rather than the wearers"" feet. (At the other extreme, some shoes in the existing art have flat midsoles and bottom soles, but have insoles that conform to the wearer""s foot sole.)
Consequently, in existing contoured shoe soles, the total shoe sole thickness of the contoured side portions, including every layer or portion, is much less than the total thickness of the sole portion directly underneath the foot, whereas in the applicant""s shoe sole inventions the shoe sole thickness of the contoured side portions are at least similar to the thickness of the sole portion directly underneath the foot.
The major and conspicuous structural difference between the applicant""s underlying concept and the existing shoe sole art is paralleled by a similarly dramatic functional difference between the two: the aforementioned equivalent or similar thickness of the applicant""s shoe sole invention maintains intact the firm lateral stability of the wearer""s foot, that stability as demonstrated when the foot is unshod and tilted out laterally in inversion to the extreme limit of the normal range of motion of the ankle joint of the foot. The sides of the applicant""s shoe sole invention extend sufficiently far up the sides of the wearer""s foot sole to maintain the lateral stability of the wearer""s foot when bare.
In addition, the applicant""s shoe sole invention maintains the natural stability and natural, uninterrupted motion of the wearer""s foot when bare throughout its normal range of wideways pronation and supination motion occurring during all load-bearing phases of locomotion of the wearer, including when the wearer is standing, walking, jogging and running, even when the foot is tilted to the extreme limit of that normal range, in contrast to unstable and inflexible conventional shoe soles, including the partially contoured existing art described above. The sides of the applicant""s shoe sole invention extend sufficiently far up the sides of the wearer""s foot sole to maintain the natural stability and uninterrupted motion of the wearer""s foot when bare. The exact thickness and material density of the shoe sole sides and their specific contour will be determined empirically for individuals and groups using standard biomechanical techniques of gait analysis to determine those combinations that best provide the barefoot stability described above.
In general, the applicant""s preferred shoe sole embodiments include the structural and material flexibility to deform in parallel to the natural deformation of the wearer""s foot sole as it is were bare and unaffected by any of the abnormal foot biomechanics created by rigid conventional shoe sole.
Directed to achieving the aforementioned objects and to overcoming problems with prior art shoes, a shoe according to the invention comprises a sole having at least a portion thereof following the contour of a theoretically ideal stability plane, and which further includes rounded edges at the finishing edge of the sole after the last point where the constant shoe sole thickness is maintained. Thus, the upper surface of the sole does not provide an unsupported portion that creates a destabilizing torque and the bottom surface does not provide an unnatural pivoting edge.
In another aspect of the invention, the shoe includes a naturally contoured sole structure exhibiting natural deformation which closely parallels the natural deformation of a foot under the same load. In a preferred embodiment, the naturally contoured side portion of the sole extends to contours underneath the load-bearing foot. In another embodiment, the sole portion is abbreviated along its sides to essential support and propulsion elements wherein those elements are combined and integrated into the same discontinuous shoe sole structural elements underneath the foot, which approximate the principal structural elements of a human foot and their natural articulation between elements. The density of the abbreviated shoe sole can be greater than the density of the material used in an unabbreviated shoe sole to compensate for increased pressure loading. The essential support elements include the base and lateral tuberosity of the calcaneus, heads of the metatarsal, and the base of the fifth metatarsal.
The shoe sole of the invention is naturally contoured, paralleling the shape of the foot in order to parallel its natural deformation, and made from a material which, when under load and tilting to the side, deforms in a manner which closely parallels that of the foot of its wearer, while retaining nearly the same amount of contact of the shoe sole with the ground as in its upright state under load.
These and other features of the invention will become apparent from the detailed description of the invention which follows.